1. Field of the Invention
This invention relates to a method and an apparatus for operating a magnetic vehicle with a long stator linear motor.
More particularly, the invention concerns a method, in which winding sections of the long stator arranged one after the other in the direction of a track and isolated electrically from one another by changeover points are connected in sequence in accordance with the progress of the magnet vehicle to a track cable serving for the current supply, and an apparatus which comprises at least one track cable extending in the direction of the track for supplying the winding sections with current, at least on substation connected to the track cable and first switching devices for sequential connection of the winding sections to the track cable in accordance with the progress of the vehicle.
2. Description of the Prior Art
In linear motors for magnet vehicles, especially in synchronous long stator linear motors for magnetically levitated vehicles, the stator winding is usually sub-divided into many short winding sections, e.g. only about 1.2 km long, lying directly one after the other in the direction of travel and electrically isolated from one another by changeover points. Moreover a comparatively long track cable, e.g. about 40 km, is laid parallel to the track and is connected to a so-called substation, in which the converters or the like required for the current supply to the stator winding are installed. In order to limit the power consumption only that winding section in which the vehicle is actually present is supplied with current, in that the individual winding sections are connected individually and sequentially to the track cable with the aid of switching devices, in accordance with the progress of the vehicle.
One problem with this control, known as the short-circuit method, of the current supply controlling the speed of the vehicle is that only one of the two winding sections adjoining a changeover point can be connected at a time to the track cable when traversing this point, since otherwise the current flow in the winding sections can no longer be controlled and the vehicle acts on the current in a manner corresponding to a short-circuit. A result of this is that there is a temporary alteration in the active vehicle length at each section change and hence a reduction in the propulsive force, which amounts to at least 50% and affects the comfort of the ride.
In order to avoid such slumps in the propulsive force many methods and apparatuses have already been proposed (e.g. offprint of etz Vol. 108, 1987, issue 9, pages 1-24, DE 3 917 058 A1), which are known under catchwords such as xe2x80x9cleapfrog methodxe2x80x9d, xe2x80x9calternate step methodxe2x80x9d, xe2x80x9cdouble feedxe2x80x9d, xe2x80x9cposition dependent current distributionxe2x80x9d or the like. A feature common to all these methods and apparatuses is however that, when passing a changeover point, either only the one or the other participating winding section is fed with current and therefore only part of the vehicle motor is active. On account of this dependence of the active part of the vehicle motor on the vehicle position in the region of the changeover points, slumps in the propulsive force could previously only be avoided in that either the power installed in the substations was over-dimensioned, in order to meet the increased demand when passing a changeover point, or separate supply systems with at least two track cable were provided.
In contrast to this it is an object of this invention to modify the method and the apparatus mentioned above such that the whole vehicle motor can always remain active in the region of the changeover points.
A further object of the invention is to design the method and the apparatus such that stator section changeovers are possible substantially without slumps in the propulsive force of the long stator motor.
Yet another object of this invention is to create new possiblities for effecting smooth changeovers of a magnetic vehicle, particularly a magnetically levitated vehicle from one long stator section to a following long stator section.
These and other objects of the invention are solved by a method which is characterized in that, before traversing any changeover point, in each case a first winding section connected to the track cable and a second winding section separated therefrom by the changeover point are connected together in an electrical series circuit and remain connected until after the changeover point has been traversed.
An apparatus according to this invention is characterized by switching devices through which two winding sections lying directly after one another in the direction of travel can be connected electrically together.
The invention provides the advantage that the two winding section involved at a changeover point are always connected in series circuit during the section change and are traversed by the same current. Accordingly, on the one hand the position of the vehicle relative to the changeover points has practically no significance, on the other hand numerous novel possibilities for the current supply when passing a changeover point result.
Further advantageons features of the invention appear from the dependent claims.